Endorphins and Thermodynamics
by AnonymousLeader
Summary: (Bruce/Tony) Bruce Banner is glad Tony Stark let him live with him in his manor, but he can't help but struggle with these emotions he's feeling. They seem so different, yet so tantalizing, and he can't tell if Tony is toying with him for fun or for something more. Rated- M for heavy smut. No fooling around, this has some graphic content.
1. Chapter 1: Thermodynamics

It had been almost half a year since Bruce Banner took the offer of a scientist's lifetime… well, if the offer included a large hadron collider and a couple kilograms of adamantium. But Tony was close to uncovering the formula held by the US government; in fact, he could've easily hacked into the database in less than five minutes. He just didn't have need of it yet. And of course Tony was already building a hadron collider underneath his home, so it was practically a perfect offer.

In the beginning he didn't expect too much, an erroneous thought of course. Bruce still went into a state of bemused bewilderment at Tony's very own person. He was a smart(ass), devil-may-care Debonair, at one moment working on an algorithm for his suit's energy conservation and another, using that suit to see if he could simultaneously pour liquor off his balcony and catch said liquor in his mouth before it hit the ground. And yet it worked for him. Bruce didn't mind of course. He appreciated the new life Tony brought into science, a profession already wrought with stereotypes of old, boring men without a daring bone in their body. Tony Stark was the bane of their dogmatic codes.

Tony appreciated Bruce's brilliant mind as well as his lack of conformity to those stereotypes, and in return, Bruce provided Tony a halfway-decent intellect to bounce his plethora of ideas off of. That was the main reason he built an extension in his workstation for Bruce's very own experiments.

At the moment, the two were working on their own respective projects. Bruce was working on a neutron emission power generator similar to Tony's arc reactor technology, though not as simple. Tony just finished with an update for JARVIS's software and was working on a program for increased accuracy with his missile defense system that protected his manor. All the while Aerosmith blasted over the loudspeakers, which typically hindered Bruce, but he grew to really enjoy the intensity of it. It helped him focus.

"So how do you feel about neutrino collisions at 300 ft? Too shallow? Or should we just screw it and have it at 129 feet?" Stark interjected as Bruce was discerning different neutron compounds.

"Does this relate to the hadron collider you're building? I thought you needed government approval for such a thing," Bruce said, looking up.

"Oh the government doesn't even know. Has no idea. Figured once I discovered how to harness dark matter, the feds wouldn't mind too much. Just give them a taste of the tech and they'll wave any infraction aside."

Bruce smirked and shook his head. "I guess radioactive decay affecting us doesn't matter either."

"Not since I installed my own little radiation protection mix. Something I cooked up awhile back. No radiation will _ever _penetrate this building," Tony said, leaning back in his chair.

"What about from inside the building?" Bruce did want to work on curing himself of this "other guy" of his, and he would need to make sure that all the precautions were observed.

"The only real threat of radiation comes from that little green friend of yours. And I think you can manage that, hell I think I can manage you managing that."

"Well can you manage to turn down the volume? I can feel my heartbeat increasing from that guitar solo," Bruce teased.

"I'm sorry but no can do. This is the best part!" Tony air-guitared the intense solo, the volume causing the glass windows to shake. Bruce smiled and continued to work.

Eventually Bruce saw Tony get up from his desk and head over to him.

"Whatcha doin Brucey Boy? Care to share your little project?" Tony said, standing behind Bruce and leaning towards the screen, observing it.

"Oh just some preliminary measurements for an idea that I've had on nuclear fission. I just can't seem to get it right though. I've gone through my calculations, checked the physics of it and everything, but it's not working out."

Tony leaned in closer—contemplating the information—and smirked. "Looks like someone's forgetting the basics of thermodynamics," Tony pointed to a portion of the calculation, "2nd law of thermodynamics can really improve reactions, you know."

Bruce was dumbfounded. How could he have forgotten? It was kindergarten material for him. Even now, Bruce could see the law working in their office space between he and Tony…

Bruce stopped.

The heat radiating off of Tony, the proximity (or lack thereof) between the two of them. He could feel the waves of heat from Tony, enveloping him like sensuous silk. It was alluring. Even now, Bruce struggled with a faint feeling that he hadn't felt in a long time. He was getting dizzy from the intoxicating heat.

"… which should resolve the issue with the initial reaction," Tony said, his body pressed against the sidearm of Bruce's chair, almost draped over Bruce himself, "Whatdaya think?"

Bruce was dazed, yet he heard the question loud and clear. "Oh uh yeah, that seems like it would work," he said. What was going on?

Nothing was going on. His good friend was just giving him advice about his project. That was all. Just two really close friends.

"Of course it will, why wouldn't it? Now about the actual…" Tony leaned in ever closer to Bruce, wrapping his arm around Bruce nonchalantly as he gestured to the screen. It almost seemed like Tony was sitting right on top of him judging by the closeness between the two. Even now, Bruce tugged at his collar, trying to get fresh air that he felt like he needed. His t-shirt felt unnaturally thin and tight, his trousers even more so.

He glanced over at Tony. How could his tank top show the muscle definition he had? That beard looked so trimmed and accentuated the already perfect features of his face. And his sweatpants filled out so nicely with that _really_ big bulge…

Bruce stopped himself. His heart was pounding. His pulse was rushing. Sweat dripped from his face, the adrenaline heightening his senses. A fight or flight response, but to what? To Tony? Was he attracted to Tony Stark? Who wasn't turned on by his dashing persona? Not him.

Yet he continued glancing over at Tony, eyeing him with anxiety. He couldn't allow himself to get too carried away. Already his heartbeat was almost to the threshold rate, meaning if he didn't do something soon, there was a chance "the other guy" might come by. He had to flee, take flight instead of fight.

His brain said this, but his body said otherwise. It was as if the intense heat and closeness between he and Tony froze him in place. The music throbbed through his body, and in response, a slow throbbing began happening in his groin. His eyes—almost separate from his brain's impulses—darted back and forth between his computer screen and the prominent bulge sticking out at his face. Tony's crotch was so close that all Bruce would have to do would be to lean a little forward, mouth open and…

Bruce shot up from his desk, startling Tony. "I'm sorry Tony, I just really need to use the bathroom," he said, excusing himself awkwardly and not making eye contact. He shuffled out of his area, almost tripping on his desk chair, and bolted out of the glass-paned room. His heart was almost jumping out of his chest, and he checked his heart rate monitor. It was one less than his threshold rate; he needed to calm himself down badly. Or else.

As he passed by, he looked inside at Tony one more time to see his eyes right on him. It was hard to tell though what meaning hid beneath those eyes. Bruce could've sworn those friendly eyes were hiding more-than-friendly ideas, but was that really what he saw or was that just another one of Tony's glares?

After about 30 minutes of breathing exercises and meditation techniques, Bruce headed back into the room to see Tony working at his desk. Tony looked up and gave another one of his smirks.

"That seemed like one long bathroom break. What were you doing in there? Dropping fully-grown adults off at the pool?" Tony quipped. Bruce only responded with a half-hearted laugh. "I took the liberty of fixing that formula for you. Should work a lot better with what you're doing, though it does require that law of thermodynamics we discussed about," Bruce sat down in his chair, nervous to respond, "Or do you need me to tutor you again in the fundamentals of thermodynamics again my nuclear physicist?"

"Nah. I'm—I'm good," Bruce could only muster. Even after all that, he could still feel Tony's heat coursing through him like warm liquor. That stare, it seemed so inviting almost. Bruce could now recall it, but he still couldn't tell whether it was something more than just a typical Tony Stark stare.

Bruce's eyes continued to steal glances at Tony, his mind trying his best to coax them not too. His heartbeat returned to a race, yet Bruce worked harder to keep it down. AC/DC blaring out their rock tunes did help on one hand, but on the other, the heavy beat and the throbbing of the music toyed with his crotch like a snake charmer tempting a trouser snake to come out. His futile attempts couldn't keep his raging erection from tenting his trousers. Hopefully Tony couldn't see his arousal, but even then as he looked up to steal one more glance, Tony was smirking at Bruce, the stare the same from the one before.

A stare that was toying with him to ask for more.


	2. Chapter 2: Dopamine

_ Okay, now I just need to sleep._

It had been over 3 hours since Bruce had tried falling asleep no to avail. No matter what sleep or meditative techniques he used, his mind continued to stay active. In 5 years of deep sleep this was the first time he had insomnia.

And it wasn't ordinary insomnia. His mind had become fixated on the thought of Tony Stark and the erotic experience that occurred just a few hours ago. Just what was that? It had been years and years since he had dated, but he wasn't that naïve. Yet the feelings he felt that time were so new, so different, so tantalizing.

_Okay I need to take my mind off of Tony. I don't want to even think about it right now. Something that keeps my mind occupied with other things would help._

Bruce decided that a word association game would take his mind off of the inappropriate thoughts he was being bombarded with. It started out simple, with elemental compounds and their derivatives. Then it evolved into complex macromolecules that affected different things. Polysaccharides, polypeptides, proteins, neurotransmitters, endorphins.

Bruce was almost asleep until the word association game ended up on dopamine, a major neurotransmitter that affected levels of happiness and sexual arousal. In times of sexual arousal, high dopamine levels would be released, leading to attraction and even addiction. Whenever Bruce was around Tony, a high level of dopamine would be released indicating attraction. It became almost a sort of addiction, that man with his broad shoulders, muscular body, a light coat of fur on his chest, those vascular legs, that delicious-looking cock…

Once again, Bruce shot up from his bed, annoyed and aroused. He could feel his hard-on aching for stimulation, the engorged member throbbing painfully against his briefs. He groaned, reaching down to adjust himself.

_Why Tony Stark? Why my best friend who let me into his home with no strings attached? Why would I even have a chance? I mean his beard must be scraggly to the touch, easy to rub my skin against. His pecs so firm and taught, his arms able to rip my shirt apart, his hard thighs wrapped around mine, his giant cock rubbing against mine…_

Bruce was slowly stroking himself, the groans becoming moans. His erection trembled at the sensations, pre-cum leaking out and staining his briefs. Bruce slipped out of his briefs and tossed them aside, the beast finally released after being caged for so long. Bruce shuddered at the waves of euphoria that washed over him as he sped up his stroking. This he had a lot of experience with.

He took some of the pre-cum leaking and rubbed it along his shaft, lubricating down to his balls. The cock jumped in response, eliciting a large moan out of Bruce.

His stroking became hardcore pounding as he cupped his hand around his cock, running up and down quickly along the shaft and down to the base. It felt so good, so delicious, so ravenous.

_Oh fuck Tony. He and his charm, that sexy persona he puts off. That playful smirk of his. What I wouldn't give for that smirk to attack my cock and suck me dry._

Bruce was nearing his orgasm. He imagined Tony coming into his room, crawling up on the bed like a predator waiting in anticipation to attack his prey, devouring his meat with ravenous hunger. He could imagine Tony frotting his massive cock against his, the two large swords dueling one another, pressing against one another. He could feel Tony brandishing that sword as a trophy, polishing it with his pre-cum, then ramming it into Bruce's sheath of an ass. Pulsating. Driving in and out in rhythmic motions before…

Release. Bruce cried out as his cock exploded with cum, covering his exposed sheets in decadence. He felt satisfied, satiated, his cock throbbing with approval.

_ If only Tony came in at that time for real._

Bruce reached out to his heart rate monitor to check. It was way above the threshold, yet Bruce didn't feel worried at all. In fact, he felt relieved. He had done this all the time, but whenever he did, he'd have to watch his heart rate to make sure he didn't let "the other guy" take over. Yet after fervent beating, "the other guy" wasn't coming out at all.

It took a full 10 minutes for Bruce to finally calm his erection down. He smiled. Maybe all he needed was a little "manual override" so to speak. Bruce turned over, underwear still off, sheets tossed to the side and immediately fell into a deep, wonderful sleep, full of sensual dreams.


End file.
